This invention relates to certain transition metal compounds from Group 4 of the Periodic Table of Elements, and to a catalyst system comprising a Group 4 transition metal compound and alumoxane, modified alumoxane, non-coordinating anion activator, Lewis acid, or the like to form an active catalyst species for the production of polyolefins such as polyethylene, polypropylene and alpha-olefin copolymers of ethylene and propylene having a high molecular weight.
Monocyclopentadienyl heteroatom compounds are now well known as components for olefin polymerization catalysts. Bimetallic and polymetallic monocyclopentadienyl-bridged polymerization catalysts are also known. Monocyclopentadienyl transition metal complexes which are bridged to another monocyclopentadienyl transition metal complex are disclosed, for example, in Ciruelos et al., Organometallics, vol. 12, pp. 944-948 (1993); Lee et al., Macromol. Rapid Commun., vol. 16, pp. 265-268 (1995); and Larkin et al., Organometallics, vol. 15, pp. 2393-2398 (1996). Ciruelos et al. also disclose direct bridging of the transition metal with an oxygen atom. Bridged monocyclopentadienyl transition metal complexes including heteroatom (amine) ligands are disclosed in Diamond et al., Organometallics, vol. 14, pp. 5-7 (1995); Diamond et al., Organometallics, vol. 15, pp. 4030-4037 (1996); Christopher et al., Organometallics, vol. 15, pp. 4038-4049 (1996); and Diamond et al., J. Am. Chem. Soc. vol. 118, pp. 8024-8033 (1996). However, none of these compounds contain bulky amine ligands.
Bis(cyclopentadienyl) transition metal complexes are bridged together via the cyclopentadienyl groups in bimetallic and polymetallic compounds described in, for example, Nomura et al., Polymer Bulletin, vol. 35, pp. 683-689 (1995); Stempfl et al., Gazzetta Chimica Italiana, vol. 125, pp. 287-290 (1995); Ushioda et al., Journal of Organometallic Chemistry, vol. 518, pp. 155-166 (1996); Lee et al., Korea Polymer Journal, vol. 4, pp. 107-111 (1996); Xu et al., Macromol. Rapid Commun., vol. 17, pp. 645-651 (1996); Diamond et al., J. Chem Soc., Dalton Trans., pp. 921-938 (1996); DE 4,446,922 (1996); EP 664,304; and U.S. Pat. No. 5,627,117 to Mukaiyama et al. U.S. Pat. Nos. 5,372,980 and 5,442,020, both to Davis, disclose bridged bis(cyclopentadienyl) transition metal complexes wherein the cyclopentadienyl groups in each complex are bridged together and two complexes are tethered together via the cyclopentadienyl groups and the bridging groups.
U.S. Pat. No. 5,444,145 to Brant et al., and U.S. Pat. No. 5,055,438 to Canich, and WO 92100333, disclose monocyclopentadienyl heteroatom transition metal complexes wherein the heteroatom is linked via a bridging group to the cyclopentadienyl group. The transition metal complexes can be bridged together directly via shared anionic ligands. Noh et al., Journal of Organometallic Chemistry, vol. 518, pp. 1-6 (1996) disclose polysiloxane-bridged binuclear and polynuclear monocyclopentadienyl transition metal compounds. U.S. Pat. No. 5,693,730 to Kxc3xcber et al. discloses polynuclear metallocene compounds wherein bridged bis(cyclopentadienyl) transition metal complexes are tethered together via the cyclopentadienyl bridging group.
The catalyst system of this invention comprises a tethered pair of cyclopentadienyl transition metal compounds from Group 4 of the Periodic Table of the Elements, activated with an alumoxane, modified alumoxane, non-coordinating anion activator, Lewis acid or the like which may be employed in a solution, slurry, bulk or gas phase polymerization procedure to prepare a polyolefin. The metal compounds have a bidentate ancillary ligand system consisting of one cyclopentadienyl group covalently bound to the metal and a heteroatom group covalently bound to the transition metal, preferably linked to the cyclopentadienyl group by a bridging group containing a Group 14-15 element. The ligands are tethered by a tethering group containing a Group 13-16 element. The tethering group can be linked through the bridging groups, or a combination of the bridging groups and heteroatom groups, provided that when the tethering group is a hydrocarbylene diradical the bridging groups are independently di-alkyl, alkylenyl or diaryl silicon or germanium radical, when the tethering group is an oxygen diradical the bridging groups are free of silicon, and when the tethering groups contain silicon, germanium, nitrogen or phosphorus the bridging group is free of carbon. The tethering group can also be linked solely through the heteroatom groups.
A typical polymerization process according to the present invention, such as the polymerization or copolymerization of olefins, comprises the steps of contacting ethylene or C3-C20 alpha-olefins alone or with other unsaturated monomers including C3-C20 alpha-olefins, C4-C20 diolefins, and/or acetylenically unsaturated monomers) either alone or in combination with other olefins and/or other unsaturated monomers, with a catalyst comprising, in a suitable polymerization diluent, the tethered monocyclopentadienyl Group 4 transition metal component of the invention; and an alumoxane, modified alumoxane, non-coordinating anion activator, Lewis acid or the like, or combinations, in an amount to provide a molar aluminum, non-coordinating anion, or Lewis acid to transition metal ratio of from about 1:1 to about 20,000:1 or more; and reacting such monomer in the presence of such catalyst system at a temperature from about xe2x88x92100xc2x0 C. to about 300xc2x0 C. for a time from about one second to about 10 hours to produce a polyolefin having a weight average molecular weight of from about 1000 or less to about 5,000,000 or more, and a molecular weight distribution of from about 1.5 to about 15.0 or greater.